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a(n) is the order of A337775(n) (as defined in that sequence).
2

%I #24 Oct 25 2020 22:52:30

%S 0,1,2,2,3,3,4,2,4,4,4,3,5,3,5,5,5,5,5,5,4,4,6,6,6,4,6,6,3,6,3,6,7,6,

%T 5,4,5,4,7,5,7,5,5,7,4,5,5,4,7,4,7,7,7,3,8,7,7,4,7,7,7,6,6,5,6,6,5,6,

%U 6,6,8,8,6,6,4,6,8,6,6,8,6,6,6,5,5,8,8,5,6,6,8,8,5,5,8,4,5

%N a(n) is the order of A337775(n) (as defined in that sequence).

%D J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 108, p. 38, Ellipses, Paris 2008.

%D J.-M. De Koninck & A. Mercier, 1001 Problèmes en Théorie Classique Des Nombres, Problème 745 ; pp 95; 317-8, Ellipses Paris 2004.

%H J.-M. De Koninck, <a href="https://www.jstor.org/stable/4145084">When the Totient Is the Product of the Squared Prime Divisors: Problem 10966</a>, Amer. Math. Monthly, 111 (2004), p. 536.

%F rad(A337775(n))^a(n) = phi(A337775(n)).

%F a(n) = log(phi(A337775(n))) / log(rad(A337775(n))). - _Andrew Howroyd_, Sep 21 2020

%t nn = 97;

%t Sar = Table[0, {nn}]; Sar[[1]] = 2;

%t (*It is a list oh the sequence A337775*)

%t OrdSar = Table[0, {nn}]; OrdSar[[1]] = 0;

%t (*It is a sequence A337776 - the orders of members in sequence A337775*) For[Index = 2, Index <= nn, Index++,

%t InitialPrime = Prime[Index];

%t InitialInteger = InitialPrime - 1;

%t InitialArray = FactorInteger[InitialInteger];

%t For[i = 1, i <= Length[InitialArray], i++,

%t CurrentArray =

%t FactorInteger[InitialArray[[-i, 1]] - 1] ~Join~ InitialArray;

%t InitialInterger =

%t Product[CurrentArray[[k, 1]] ^ CurrentArray[[k, 2]], {k, 1,

%t Length[CurrentArray]}];

%t InitialArray = FactorInteger[InitialInterger];

%t ];

%t InitialArray = InitialArray ~Join~ {{InitialPrime, 0}};

%t Ord = Max[InitialArray[[All, 2]]];

%t Lint = Product[

%t Power[InitialArray[[k, 1]], Ord - InitialArray[[k, 2]] + 1], {k,

%t 1, Length[InitialArray]}];

%t radn = Product[InitialArray[[k, 1]], {k, 1, Length[InitialArray]}];

%t Sar[[Index]] = Lint;

%t OrdSar[[Index]] = Ord;

%t ];

%t Print["Sar= ", Sar]

%t Print["OrdSar= ", OrdSar]

%Y Cf. A000010 (phi), A000040 (prime), A007947 (rad), A337775.

%K nonn

%O 1,3

%A _Vladislav Shubin_, Sep 20 2020